Plotting in R (scatter plot, multicolor and linear regression) - Part 1

Plot is the most basic grapphing function in R. I typically use it as a scatter plot to look for a relationship between two variables. The classic example of this is uses the build in data set in R called cars which measures the braking distance of a car versus its speed.

speed<-c(4,4,7,7,8,9,10,10,10,11,11,12,12,12,12,13,13,13,13,14,14,14,14,15,15,15,16,16,17,17,17,17,18,18,18,19,19,19,20,20,20,20,20,22,23,24,24,24,24,25)
dist<-c(2,10,4,22,16,10,18,26,34,17,28,14,20,24,28,26,34,34,46,26,36,60,80,20,26,54,32,40,32,40,50,42,56,76,84,36,46,68,32,48,52,56,64,66,54,70,92,93,120,85)
car<-as.data.frame(cbind(speed,dist))
plot(car)

R’s format is very flexible. We could have also done plot(dist~speed,cars) or plot(cars[,1],cars[,2]) and gotten exact the same plot.

To test for a linear regression we might as well add the regression line to the plot

plot(car)
abline(lm(dist~speed,car))

Rarely in recent times is a data set so small. Most data sets we see today are large and messier than this one.